1. Field of the Invention
This invention relates to a separable slide fastener which comprises a pair of fastener tapes, a pair of fastener-element assemblies attached to confronting longitudinal edges of the fastener tapes by sewing, each fastener-element assembly having a succession of fastener elements molded on a pair of parallel connecting yarns at regular distances and folded individually into a U-shape about each of confronting longitudinal edges of the fastener tapes, and an insertion pin and a box pin attached to bottom end portions of the respective fastener tapes.
2. Description of the Related Art
Japanese Utility Model Laid-Open Publication No. Hei 4-125708 discloses a separable slide fastener which comprises a pair of fastener tapes, a pair of fastener-element assemblies attached to confronting longitudinal edges of the fastener tapes by sewing threads, and a separable bottom stop assembly attached to confronting bottom end portions of the fastener tapes. Each fastener-element assembly is composed of a succession of fastener elements extrusion-molded on a pair of parallel connecting yarns in such a manner that the connecting yarns are embedded in upper and lower legs, respectively, of the successive fastener elements. The individual fastener elements of each fastener-element assembly are folded in a U-shape about the inner longitudinal edge of the corresponding fastener tape. Each fastener tape has along its inner longitudinal edge a bulged portion to which the legs of the successive fastener elements are attached by the sewing threads. The bottom end portion of each fastener tape is formed by removing several fastener elements. An insertion pin of the bottom stop assembly is attached to the fastener-element-free bottom end portion of one fastener tape, and a box pin is attached to the fastener-element-free bottom end portion of the other fastener tape.
Japanese Patent Laid-Open Publication No. Hei 7-79815 discloses another separable slide fastener which comprises a pair of fastener tapes, a pair of fastener-element assemblies attached to confronting longitudinal edges of the fastener tapes by sewing threads, and a separable bottom stop assembly attached to confronting bottom end portions of the fastener tapes. Each fastener tape is woven so as to form along its inner longitudinal edge a bulged portion in the form of a woven tube in which a plurality of core yarns are inserted. Each fastener-element assembly is composed of a succession of thermoplastic resin fastener elements extrusion-molded on a pair of parallel connecting yarns and folded individually in a U-shape about the inner longitudinal edge of each fastener tape; upper and lower legs of the fastener element are sewn to the bulged portion so as to clamp the bulged portion between them. An insertion pin of the bottom stop assembly is attached to the bulged bottom end portion of one fastener tape contiguously to the lowermost fastener element, and a box pin is attached to the bulged bottom end portion of the other fastener tape contiguously to the lowermost fastener element.
In conventional extrusion-molded slide fasteners, since the insertion pin or the box pin of the separable bottom stop assembly is attached to the longitudinal edge of each fastener tape so as to merely cover the sewing threads after cutting the connecting yarns of the fastener-element assembly, stable attachment of the bottom stop assembly members is difficult to achieve so that these members might be removed of the fastener tapes.
A solution has been proposed by the first-named publication. According to this solution, in an attempt to attach the fastener elements to the bulged longitudinal edges of the fastener tapes stably, a pair of grooves are formed in the inner surfaces of the upper and lower legs of each fastener element, and the individual fastener elements are attached to the bulged longitudinal edges of the fastener tapes by sewing with the bulged portion fitted in the grooves of the legs. The bottom end portion of each fastener tape is formed by cutting the connecting yarns to remove several fastener elements, whereupon the insertion pin or the box pin is attached to the element-free bulged portion at the bottom end portion of each fastener tape. With this structure, however, a gap is created at the boundary of the lowermost fastener element and the insertion pin or box pin so that the coupled fastener element rows would tend to split from the boundary. Further, because of the bulged portion, it is difficult to thread the fastener-element assembly onto the fastener tape edge when sewing the fastener elements to the fastener tape, which is laborious and time-consuming.
According to another solution proposed by the second-named publication, the bulged portion of the fastener tape edge is modified in an attempt to facilitate sewing the fastener-element assembly to the fastener tape edge. However, because of the core yarns, it is difficult to smoothly thread the fastener-element assembly onto the fastener tape edge so that an improved rate of production cannot be achieved. Further, since the insertion pin or the box pin are attached to the bottom end portion of each fastener tape contiguously to the lowermost fastener element by molding, a gap is created at the boundary between the lowermost fastener element and the insertion pin or box pin so that the coupled fastener element rows would tend to split from the boundary.